Poultry Litter Gasification in a Fluidized Bed Reactor: Effects of Gasifying Agent and Limestone Addition

Air and air-steam gasification of poultry litter was experimentally studied in a laboratory scale bubbling fluidized bed gasifier at atmospheric pressure using silica sand as the bed material. The effects of equivalence ratio (ER), gasifier temperature, steam-to-biomass ratio (SBR), and addition of limestone blended with the poultry litter, on product gas species yields and process efficiency, are discussed. The optimum conditions (maximum carbon conversion, gas yield, heating value, and cold gas efficiency) were achieved at an ER 0.25 and 800 °C, using air (SBR = 0) and poultry litter blended with 8% w/w limestone, yielding a product gas with a lower heating value (LHV) of 4.52 MJ/Nm 3 and an average product gas composition (dry basis) of H 2 : 10.78%, CO: 9.38%, CH 4 : 2.61, and CO 2 : 13.13. Under these optimum processing conditions, the cold gas efficiency, carbon conversion efficiency, and hydrogen conversion efficiency were 89, 73, and 43% respectively. The reported NH 3 measurement at an ER of 0.28 and 750 °C is 2.7% (equivalent to 19,300 mg/Nm 3 ) with 14.7 mg/Nm 3 of HCl observed as the dry product gas. High temperature and steam injection favor production of CO and H 2 , while their effect on CH 4 was almost negligible. It is demonstrated that poultry litter can be gasified by blending with limestone, making it possible to overcome the fluidization problems caused by the mineral composition of poultry litter ash (high K and P content), yielding a gas with a similar heating value compared to gasifying without limestone addition, but with a significantly lower tar content

Unsuccessful predation on Middle Paleozoic plankton: Shell injury and anomalies in Devonian dacryoconarid tentaculites

Anomalous development of shell ornamentation and repaired shell injury in the Early Devonian dacryoconarid tentaculites are documented and interpreted as either a repaired injury of the shell (evidence of unsuccessful predation obscured by recrystallization), or as a result of an anomalous function of the mantle, caused by injury of the soft body. The manner of shell repair, which resembles the way that some modern marine animals, such as mollusks, repair their shells, is discussed. The issue of phylogenetic affinities of tentaculites has been also outlined. These findings represent the first documentation of unsuccessful predation on the Middle Paleozoic plankton